An Indian court denied bail on Saturday to two Italian marines charged with the murder of two fishermen who were shot dead off the country's southwestern coast.
The move came a day after murder charges were laid against the marines and Rome recalled its ambassador from New Delhi for "consultations" over the case.
The marines deny the charges, saying they mistook the fishermen for pirates.
Massimiliano Latorre and Salvatore Girone were deployed as guards on an Italian oil tanker in the Indian Ocean when they shot dead the two fishermen on February 15.
The marines, who have been held in prison for three months, were denied bail at a court in Kollam, a city in the southwest corner of the coastal state of Kerala.
The judge said he accepted the prosecution's argument that bail should be refused on the grounds the accused might seek to influence witnesses or flee the country.
He called for a "speedy trial" in order to "deliver natural justice in the case".
In response to the charges, the foreign ministry in Rome said on Friday: "The Italian ambassador to New Delhi has been recalled to Rome for consultations on the matter of the marines."
Syed Akbaruddin, spokesman for the Indian foreign ministry, told AFP: "We have consistently said that this is a legal process and the law of the land should take its course."
"We are aware that Italy has called back its ambassador for consultations but we are not going to comment on their reaction to what remains a legal process."
India has said in the past that the two countries "have the maturity to address this challenge together" and that the case should not affect good bilateral relations.
The Italian government has paid compensation of 144,000 euros ($190,000) to the families of Selestian Valentine, 45, and Ajesh Pinky, 24, but that has done little to stop the diplomatic row escalating.
Italy has called the detention of the marines illegal and challenged it before India's Supreme Court.
Rome says the marines should be prosecuted in their home country because the shootings occurred on an Italian-flagged vessel in international waters, but India says they took place in waters under its jurisdiction.
Italy also accused the Indian fishing crew of behaving aggressively and said they were repeatedly warned before shots were fired.
The fishing boat's owner said the marines fired without provocation.
Armed guards are increasingly deployed on cargo ships and tankers in the Indian Ocean to tackle threats from Somali pirates, who often hold ships and crews hostage for months demanding multi-million dollar ransoms.